The hike starts at the Nature Center in Makiki where there is a bathroom and water. Parking is down the road from the Nature Center in a gravel lot on the left.
Since this is a loop, it can be done in the clockwise direction (starting with the Kanealole Trail) or counterclockwise (starting with the Maunalaha Trail). The latter option gets the pulse climbing more quickly because of the climbing commences right away and with greater steepness. Most times, I prefer to get the hard stuff out of the way right off the bat.
Eventually, the Moleka Trail ends at a crossing of Round Top Drive. Directly across Round Top is the start of the Manoa Cliffs Trail. The cliffy part of the trail doesn't start right away but in about 5 to 10 minutes it will.
Much of the cliff trail isn't really cliffy but there will be some nice views down into Manoa Valley along the way. The trail in this direction climbs gradually to make its way around Tantalus mountain. along the way at a sometimes windy lookout, there is a rest bench. I use this bench as a benchmark for my conditioning. If I can reach the bench from the Nature Center (via Maunalaha) in an hour, I'm moving at a good pace for me. The downhill part of the Manoa Cliff trail begins at a metal gate, which marks the entrance of an inclosed area to protect native plants.
The cliffs trail switches back several times to descend to the Kalawahine Trail. At that junction, head left and follow Kalawahine as it contours on the Ewa-facing side of Tantalus. The Kalawahine Trail ends at Tantalus Drive. To continue the loop, proceed straight ahead on Tantalus Drive for about 60-70 meters. On the left will be the Nahuina Trail which is accessed by hopping over a metal guardrail along Tantalus Drive.
Nahuina descends in switchbacks to a junction with the Makiki Valley Trail. At that junction, head left to continue the descent to the valley bottom. In a few minutes, the MVT will reach yet again another junction (this hike is big on junctions!). At that point, head right down the Kanealole Trail which ends at the Nature Center.
On good days (for me), I've done this loop in two hours. I will admit that I jog part of the flat and downhill sections of most of the route.
For a shorter (1-hour) option, the Makiki Valley Loop is a good choice. The variation on the route I described would be to head leftward instead of straight and up at the big junction to continue on the Makiki Valley Trail. Then at the junction with the Kanealole Trail, head down to return to the Nature Center.